The present invention relates to an absorbent article particularly suited for everyday feminine hygiene and for protecting an undergarment against staining from light, daily secretions and discharges. It comprises a very thin, lightweight, highly absorbent pad which is soft, supple and easily conformable to the body and the garment to which it is adhesively attached.
The prior art is replete with patents relating to protective pads and shields since the protection of undergarments from staining, especially for the many women who are troubled with frequent, light bodily discharges, has been a long standing problem. These patents generally describe layered structures having a porous body contacting layer overlying, a liquid impermeable garment side barrier layer, and a layer of absorbent material between the body contacting layer and the barrier layer. An adhesive is attached to the garment side or the fluid barrier to secure the assembled shield to the crotch portion of an undergarment. And, a release layer is removable affixed to the adhesive layer to keep the adhesive from making contact to anything until it is placed in the undergarment.
While such prior art pads undoubtedly function to protect the undergarments to which they are applied, they are deficient in one primary area of performance. They tend to draw fluid toward the lateral and longitudinal edges of the pad, increasing the likelihood of failure by allowing leakage off the pad onto the wearer's clothes.
Some body-contacting layers of the prior art which are absorbent, porous, dry-laid, nonwoven webs or scrim type materials such as those described by I. S. Ness in U.S. Pat. No. 4,880,419 and by Campau in U.S. Pat. No. 3,044,467, Hendricks in U.S. Pat. No. 3,463,154 and Sneider in U.S. Pat. No. 3,570,491. Such materials are often coarse textured and harsh to the touch and, because of their absorbency, wet from the top surface down during use resulting in a constantly moist surface against the skin.
There are also some body-contacting layers of the prior art such as those described by T. J. Luceri in U.S. Pat. No. 4,795,455, by S. Cadieux in E.P. Pat. No. 354,502, by A. T. Mays in E.P. Pat. No. 70,163, and by R. P. James in U.S. Pat. No. 4,368,323 which are nonwovens made from hydrophobic fibers which have been coated with an adhesive or have been subjected to heat and/or pressure to fuse the individual fibers to each other. Such materials tend to have only limited absorption but serve to allow passage to lower layers for absorption and retention. As a result, the fluid is wicked away from the body, leaving the surface of the body-contacting layer feeling dryer to the touch.
The use of hydrophobic fibers for the body contacting layer allows fluid to pass through to the absorbent layer beneath yet will not retain moisture on the surface layer, thus providing greater comfort to the wearer by feeling dry for a longer period of time. The desirability of such a feature has been recognized by Levesque U.S. Pat. No. 3,838,692 who describes a chemical method of providing porosity to hydrophobic materials.
The absorbent layers taught by the prior art usually consists of pulp fluff as described by S. L. Kopolow in U.S. Pat. No. 4,552,618 and 4,555,192, by D. C. Holtman in U.S. Pat. No. 4,544,596 and 4,536,432, by P. K. Chatterjee in U.S. Pat. No. 4,474,949.
Alternatively, the absorbent layer of the prior art may consist of blends of pulp fluff and synthetic fibers as described by Malaney in U.S. Pat. No. 4,756,786 and in 4,684,570. Or, the absorbent layer may be thermoplastic fibers co-formed with pulp fibers.
It is also possible to disperse into the absorbent layer a super absorbent polymer such as those taught by S. Dabi in U.S. Pat. No. 4,494,963, by I. S. Ness in U.S. Pat. No. 4,880,419 and by J. Roller in U.S. Pat. No. 4,443,492.
The liquid impermeable barrier layer, located between the absorbent layer and the garment, is commonly made of polyethylene, polypropylene, or a like material. Such layers are taught in U.S. Pat. No. 4,731,066 by R. Korpman.
Generally, the earlier prior art teaches absorbent pads made of wood pulp fluff that, when properly manufactured to absorb large quantities of fluid, are thick and bulky. Recent developments in the art teach the use of materials such as sphagnum peat moss (such as that taught by Y. Levesque in U.S. Pat. No. 4,507,122) and super absorbent polymers which, pound for pound, absorb much greater quantities of fluid than pulp allowing for the manufacture of much thinner absorbent pads.
The prior art also teaches the application of heat and/or pressure to bind the fibers of the absorbent layer together into densified areas. As fluid makes contact with such densified areas, the fluid tends to wick across the layer, away from the point of fluid introduction. This action helps to inhibit local saturation of the pad which is one cause of pad failure. See, for example, U.S. Pat. No. 4,059,114 to Richards and U.S. Pat. No. 4,886,697 to Perdelwitz et al.
Once fluid has been introduced to the body contacting surface, pad construction is designed to cause the fluid to flow into the absorbent layer and remain there until disposal of the pad. However, the garment side of the structure is usually made with a liquid impermeable barrier layer which, in the event fluid continues to flow through the pad to the garment side, prevents leakage onto the wearer's garments.
Viewing this prior art, however, it is readily apparent that little thought has been given toward keeping the fluid from migrating to the lateral and longitudinal edges of the absorbent pad. While transverse wicking takes place, the design of the densified areas is such that the fluid is not prevented, in fact it may be encouraged, to flow away from the point of fluid introduction in the center of the pad to the edges of the pad increasing the chances of failure. While perimeter barriers have been taught by the prior art, there exists a need to wick fluid from the point of introduction on the pad yet still keep it compartmentalized so that it is prohibited, or at least hindered, from flowing toward the edge of the pad. The present invention meets this and other objectives which will become apparent.